The invention is generally related to the field of interconnect layers in semiconductor devices and more specifically to aluminum interconnect layers.
As the density of semiconductor devices increases, the demands on interconnect layers for connecting the semiconductor devices to each other also increases. In a conventional interconnect process, the aluminum (and any barrier metals) are deposited, patterned, and etched to form the interconnect lines. A thick oxide liner is then deposited over the interconnect lines to eliminate metal line corrosion and line-to-line leakage when spin-on low-k dielectrics or vapor deposited dielectrics are used between metal lines. These deposited oxide liners are typically on the order of 300 xc3x85 thick. This thickness is needed to ensure the required barrier protection.
After the oxide liner is deposited, an interlevel dielectric (ILD) is formed between the interconnect lines. In order to meet the performance demands (i.e., reduced capacitance) of the interconnect lines, spin-on low dielectric constant (low-k) materials and vapor deposited dielectrics are being employed in at least some portion of the ILD. Low-k materials are generally defined as those materials having a dielectric constant below that of silicon dioxide.
There is a desire to decrease the spacing between interconnect lines as the semiconductor devices become denser. The deposited diffusion barrier on the sidewalls of the aluminum interconnect lines further reduces the spacing between interconnect lines. This, in turn, reduces the amount of low-k material that can be used for gap fill between the interconnect lines.
The invention is an aluminum interconnect line having an aluminum nitride surface layer. After the aluminum is deposited, a native aluminum oxide will typically form on the surface. An aluminum nitride surface layer is formed by converting the native aluminum oxide to aluminum nitride by using independent nitrogen and hydrogen flows in a plasma. Independent nitrogen and hydrogen flows reduce the energy barrier compared to an ammonia plasma chemistry. In addition, the ability to separately adjust the nitrogen and hydrogen flow rates provides more control over the reaction kinetics and energetics.
These and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.